The long-range goal of this research is to identify functions of unknown genes in Porphyromonas gingivalis using high-throughput bioinformatic tools. The objective of this application is to use DNA microarray technology to identify the functional classes of these unknown genes. Sequencing of the P. gingivalis genome has been completed, but 49% of the open reading frames (1003 out of 2043) have no assigned function. In this study DNA microarray technology will be used to collect global gene expression profiles under various in vitro growth conditions. These profiles will be used in four specific aims: 1) Confirmation of the expression of predicted ORFs in P. gingivalis; 2) Functional class inference of the unknown genes by clustering analysis; 3) Identification of conserved transcription regulatory motifs (such as promoters) from co-regulated genes; and 4) Establishment of P. gingivalis microarray database for public retrieval and deposit of array data. Better understanding of the unknown genes in this periodontal pathogen will lead to the development of new therapeutic strategies for periodontal diseases based on the new potential targets for novel drug and vaccine design.